Numerical simulations of the atmospheric kinetic energy spectrum (INVITED)

Abstract eng:
Idealized numerical simulations of the atmospheric kinetic energy spectrum are analyzed to better understand the wide range of results reported in the literature. In particular, the role of stratified turbulence, vertical mixing, and vertical grid resolution are investigated in simulations forced by baroclinic instability. Spectra are converged when the vertical grid spacing ∆z < 200 m – which is quite high by comprehensive atmospheric model standards – but are very sensitive to resolution with coarser grids. When the vertical mixing scheme is weak, the under-resolved spectra are energized in the mesoscale. By contrast, when strong mixing is employed, the under-resolved mesoscale cascade is suppressed. Convergence requires that vertical scales associated with the full range of horizontal scales – including quasi-geostrophic scales of large-scale vortices and the buoyancy-scale of small-scale stratified turbulence – be resolved.

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